S-IC
Boeing received the contract to build the S-IC stage on the 15th of December 1961. Engineers at the Marshall Space Flight Center had already decided on the general design before that date. The main manufacturing site became the Michoud Assembly Facility in New Orleans. Wind tunnel testing occurred in Seattle while tool machining happened in Wichita, Kansas. It took roughly seven to nine months just to build the tanks alone. A complete stage required about fourteen months of work from start to finish. Boeing produced a test model designated S-IC-D as their first stage. They also built an additional test stage called S-IC-F for facilities testing. NASA ordered fifteen flight stages numbered one through fifteen to support the initial Apollo program. In July 1967 they awarded Boeing a contract for long-lead items needed for stages sixteen and seventeen. A full contract for building stages sixteen through twenty-five was drafted during mid-1967. Budgetary restrictions caused all stages past number fifteen to be canceled altogether in October of that year.
The five F-1 engines ignited in three staggered events rather than all at once. The center engine fired first followed by a diagonal pair of outer engines. Then the remaining two outer engines ignited seconds later. These three ignition events separated by just three hundred milliseconds each. This staggered approach lessened loads on the thrust structure significantly. An instantaneous ignition of all five engines would have imparted immense stress on the stage. The four anchors held down the rocket as it built thrust during launch. These anchors were among the largest aluminum forgings produced in the United States at the time. Each anchor measured ten feet long and weighed over thirty thousand pounds. The four stabilizing fins withstood temperatures reaching negative two hundred degrees Fahrenheit. The center engine remained fixed in position while the four outer engines could hydraulically gimbal. This movement allowed engineers to control the rocket's direction during flight.
The liquid oxygen tank presented special issues for the designers of the S-IC stage. Lines through which LOX ran to the engine had to remain perfectly straight. Any bend would slow the flow of LOX and necessitate even larger and heavier piping. Therefore these lines had to pass directly through the fuel tank below. Engineers insulated these lines inside a tunnel to stop fuel from freezing to the outside. They also added five extra holes in the top of the fuel tank to accommodate this path. Nitrogen bubbled through the tank before launch to keep the fuel mixed properly. During flight the fuel was pressurized using helium stored in tanks within the liquid oxygen tank above. Both the thrust structure and fuel tank featured alternating black and white paint patterns. This visual scheme helped monitor the vehicle's roll during actual flight operations. The propellant tanks themselves were manufactured from 2219-series aluminum panels. The interstage forward skirt and thrust structure used 7075-series aluminum instead.
MSFC built two test stages designated S-IC-S and S-IC-T before any flight models existed. The structural test stage consisted of various subassemblies but never fully assembled into a complete unit. The static test stage underwent at least twenty-two test firings between 1965 and 1967. This first all-up S-IC stage earned the nickname T-Bird during its assembly period. It took place between 1963 and 1965 at the Michoud facility. Facilities testing for checking out launch complex assembly buildings occurred with stage S-IC-F. That unit returned to MSFC for storage after testing concluded then later got scrapped. Ground test dynamics model S-IC-D now resides at the U.S. Space & Rocket Center in Huntsville Alabama. Stage S-IC-1 flew on Apollo 4 on the 9th of November 1967. It was manufactured by MSFC rather than Boeing like subsequent units. Stage S-IC-2 carried TV cameras on the boattail and forward skirt during Apollo 6. A team financed by Jeff Bezos recovered one or more engines from stage S-IC-6 used on Apollo 11.
Fifteen flight stages numbered one through fifteen supported the initial Apollo program missions. Stage S-IC-3 weighed less than previously manufactured units allowing thirty-six kilograms of extra payload. This lighter weight came from a new manufacturing process introduced by Boeing. The last flight for S-IC research and development instrumentation occurred on Apollo 10. Stage S-IC-10 only carried four retrorockets in two diagonally opposite compartments instead of eight. Later missions returned to having all eight retrorockets installed as originally planned. Stage S-IC-13 changed engine shutoff timing to reduce loads on the Apollo Telescope Mount. Unused stage S-IC-14 sat on display at Johnson Space Center after being scheduled to fly Apollo 18. That mission never happened due to budget cuts ending the program early. Stage S-IC-15 remained unused until June 2016 when it moved to INFINITY Space Center in Mississippi. It was designated but never used as a backup Skylab launch vehicle. Stages sixteen through twenty-five were canceled before assembly could begin during long-lead item procurement.
A full contract for building stages sixteen through twenty-five was drafted throughout mid-1967. Budgetary restrictions caused all stages past number fifteen to be canceled altogether in October of that year. These cancelled stages would have been utilized for follow-on Apollo missions including those from the Apollo Applications Program. A 1960 study proposed a version with eight F-1 engines intended for the Saturn C-8 vehicle. Another 1961 study featured five F-1 engines designed for the Saturn C-3B and Saturn C-3BN concepts. Engineers also studied a five-engine configuration for the Saturn C-4B rocket system. A 1965 study explored reduced length and structural weight options under the name Saturn IC-Flat Bulkhead. Later proposals included a reusable booster design called Saturn S-IC-TLB stage featuring two F-1 engines. A single engine concept named Saturn S-ID Sustainer-1 emerged in 1967 as part of a stage and a half configuration. Four-engine studies appeared in 1968 for recoverable boosters intended for Saturn V-B and Saturn V-C variants.
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Common questions
When did Boeing receive the contract to build the S-IC stage?
Boeing received the contract to build the S-IC stage on the 15th of December 1961. Engineers at the Marshall Space Flight Center had already decided on the general design before that date.
Where was the main manufacturing site for the S-IC stage located?
The main manufacturing site became the Michoud Assembly Facility in New Orleans. Wind tunnel testing occurred in Seattle while tool machining happened in Wichita, Kansas.
How many F-1 engines were installed on the S-IC stage and how did they ignite?
Five F-1 engines ignited in three staggered events rather than all at once. The center engine fired first followed by a diagonal pair of outer engines then seconds later the remaining two outer engines ignited.
What materials were used to construct the propellant tanks of the S-IC stage?
The propellant tanks themselves were manufactured from 2219-series aluminum panels. The interstage forward skirt and thrust structure used 7075-series aluminum instead.
Which Apollo missions utilized flight stages numbered one through fifteen?
NASA ordered fifteen flight stages numbered one through fifteen to support the initial Apollo program. Stage S-IC-1 flew on Apollo 4 on the 9th of November 1967 and Stage S-IC-2 carried TV cameras during Apollo 6.
Why were stages sixteen through twenty-five canceled before assembly began?
Budgetary restrictions caused all stages past number fifteen to be canceled altogether in October of that year. A full contract for building stages sixteen through twenty-five was drafted throughout mid-1967 but never executed due to these cuts.